1. Field of the Invention
This invention relates to an automatic transmission locking mechanism for an automatic transmission of a vehicle, particularly for an automatic transmission of a reduced axial dimension for a vehicle.
2. Description of the Prior Art
In most front-engine front-drive automobiles (designated as "FF automobiles" hereinafter), the engine is mounted transversely. Accordingly, the axial dimension of an automatic transmission for an FF autombile is required to be reduced, particularly when the engine is mounted transversely.
Most conventional automatic transmission locking mechanisms interlocked with a manual shift lever employ the following constitution. That is, a lever is joined integrally to a manual shaft which is turned through the manual operation of a manual shift lever, the rear end of a cam rod provided intermediately with a cam is linked to the lever, a pawl with a detent is pushed up when the cam is caused to run on a slope formed in a bracket supporting the front portion of the cam rod extending forward from the cam, whereby the detent engages with a parking gear fixed to the output shaft of the transmission to lock the output shaft. A spring mechanism is provided in order to retain the pawl provided with the detent away from the parking gear to prevent the accidental contact between the detent and the parking gear during running. According to the prior art, such a spring mechanism has been constituted in a type in which the pawl having a detent is retained by the resilience of a torsion spring mounted round a shaft on which the pawl having a detent is turned and engaged at one end thereof with the pawl and at the other end thereof with a case or in a type in which the pawl having a detent is retained by the resilience of a coil spring joined at one end thereof to the free end portion of the pawl and fixed at the other end thereof to a case. The former type require a shaft of an increased length on which the pawl is turned to mount a torsion spring thereon, which increases the axial dimension of the mechanism, besides, a strong torsion spring is necessary. The latter type require a wide space within a plane in which the pawl turns due to the use of a coil spring. Furthermore, since one end of the spring is engaged with or fixed to the unfinished surface of a case in either type, the effective resilience of the spring changes between assemblies.